Teens are totally divided on this social media star who could be the next Justin Bieber

Instagram/jacobsartorius

I ask Jillian, 14, a soon-to-be high school freshman, what she thinks of that up-and-coming social media star star, uhh, what's his name? Jacob ...

"Sartorius!" she finishes, with a groan. Yes, Jacob Sartorius. "Everybody either loves him or hates him."

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If you're not a part of the "everybody" that she refers to, it could be because you're not familiar with Musical.ly, the fast-rising video network that has captured over 90 million users, mostly teens. People upload 15-second videos of themselves mouthing the words to popular songs, dancing, or performing comedy skits.

In the year since he's become famous, 13-year-old Sartorius has amassed an international following that includes millions of fans across Musical.ly, Instagram, and Vine; two pop singles; and an online merch store that includes sportswear with his name emblazoned.

Sartorius claims 8.5 million fans on Musical.ly alone, but there are millions more who have a different opinion about the young star. That's because his talents are, well, limited - though he does have two songs of his own, he's known for lip-syncing. Sartorius is not the only Musical.ly star who's been lambasted for "being famous for nothing."

Most of Sartorius' videos show him serenading the selfie camera in his bathroom or bedroom. He draws hearts with his hands and makes other hand signals to go along with the song's lyrics.

"I don't care that much for him," Jillian goes on. "I just think he's too conceited. He's one of those guys that's in your school that everybody just kind of knows is trouble and gets any girl."

Another teen I spoke with, Rachel, 13, says she thinks it's cool Sartorius is her age and already a celebrity. Her class played his single, "Sweatshirt," which debuted in May, aloud in math class.

Business Insider wrote to the young star after his return from a family vacation, to learn more about his relationship with fans (and haters). He responded shortly and sweetly, with the email-etiquette one might expect from a 13-year-old media mogul.

"I have always had an interest in music and acting that started around [age] 8, when I was doing musical theater," Sartorius explains. "When Vine and Musical.ly came along, it gave me another way to perform and express myself. I am just being me and having fun and am happy that so many people are enjoying it."

For anyone who grew up subscribing to "Tiger Beat" or plastering their bedroom walls with N*Sync posters, the appeal is obvious. Sartorius meets all the criteria of a boy-band heartthrob: He's cute, with floppy hair and puppy dog eyes. He's often pictured biting his lip or tugging at the neckline of his T-shirt. He's sexually appealing to young girls, but not in a dangerous, XXX-rated way.

Watching his videos, his massive following starts to makes sense.

In July, some 300,000 teens and their reluctant parents descended on Anaheim, California, for an annual YouTube-sponsored convention called VidCon. Musical.ly set up a booth on the exhibition floor and rotated in star users every half hour to entertain fans.

When Sartorius came on for his shift, teens mobbed the booth, according to Alex Hofmann, president of Musical.ly North America. Their screams blew through the permitted decibel levels in the auditorium. VidCon shut down the meet-and-greet and made room for him on the schedule to perform on the main stage later in the day.

"We walked Jacob out of the arena - there was a glass door next to it - and you saw all these teenagers running, hammering on the glass door, screaming Jacob's name," Hofmann tells Business Insider. "He's become a huge celebrity."

Still, there are plenty of hold-outs who reject Sartorius' insta-fame. They argue lip-syncing is something anyone can do well in the car or after a few drinks.

There's also some controversy around how the star treats his fans, as first reported by BuzzFeed.

One young woman approached Sartorius for a hug at a meet-and-greet and tweeted that he looked "disgusted" at her size. Having watched a video of the interaction, I think she might be exaggerating, but, okay.

Another fan allegedly asked Sartorius to give a shoutout to her three friends (because, teens), to which he said he couldn't possibly remember three names. The tweet has since been deleted.

Sartorius tells Business Insider that meet-ups with his fans are his favorite part of the gig.

"Every person I meet is so cool and special," Sartorius says. "I have done so many meet and greets and the fans that meet me in person know that I am down-to-earth and nice. I get so much happiness from their interactions which is why I continue to do this."

Last spring, Sartorius forayed into the music industry with two singles, "Sweatshirt" and "Hit or Miss." They have yet to find mainstream success, though "Sweatshirt" cracked the top 10 chart on iTunes - a feat most artists can only dream of. His voice lends a natural falsetto, thanks to impending puberty, but he's no John Legend.

Growing up under the spotlight has its perks, but we're guessing that internet debates about your talent and likeability are not among them. Sartorius credits his family for supporting him as he manages his newfound fame and the public scrutiny that comes with it.

"People can get famous for pretty much everything," a fan named Rachel tells me. "I like him. I'm not sure if everyone loves him."